In the Linux kernel, the following vulnerability has been resolved:
iommu/amd: Remove latent out-of-bounds access in IOMMU debugfs
In iommu_mmio_write() and iommu_capability_write(), the variables dbg_mmio_offset and dbg_cap_offset are declared as int. However, they are populated using kstrtou32_from_user(). If a user provides a sufficiently large value, it can become a negative integer.
Prior to this patch, the AMD IOMMU debugfs implementation was already protected by different mechanisms.
- #define OFS_IN_SZ 8 ensures the user string <= 8 bytes, so
if (cnt > OFS_IN_SZ) return -EINVAL;
- Implicit type promotion in iommu_mmio_write(), dbg_mmio_offset is int
if (dbg_mmio_offset > iommu->mmio_phys_end - sizeof(u64)) return -EINVAL;
- The show handlers would currently catch the negative number and
Replace kstrtou32_from_user() with kstrtos32_from_user() to parse the input, and check for negative values to explicitly prevent out-of-bounds memory accesses directly in iommu_mmio_write() and iommu_capability_write().